Brain scans reveal how gut talks to brain in obesity

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Aged 18-45, male and female (females will have the study days arranged during the early phase of the menstrual cycle). * Body mass index (BMI): normal weight participants ≥ 19 and ≤ 25 Kg/m2, and obese participants \> 30 Kg/m2 * Able to give voluntary written informed consent to participate in the study * Able to understand the requirements of the study * Apparently healthy: no medical conditions which might affect study measurements (judged by health questionnaire, and blood screening) Exclusion Criteria: * Any reported history of neurological or gastrointestinal disorders * Any reported history of surgery that could affect gastrointestinal function (e.g. colectomy, small bowel resection) * Abnormal screening procedures including depression and eat restriction * Laboratory results that are clinically significant, including diabetes, dyslipidemia, pancreatitis, or untreated hypertension. * Contraindications for MRI scanning i.e. metallic implants, pacemakers, history of metallic foreign body in eye(s) and penetrating eye injury, assessed by standard MRI safety questionnaire. * Under medication (expect aspirin/paracetamol), antibiotic or prescribed probiotic treatment in the past 12 weeks. * Following a medically- or self-prescribed diet during the two weeks prior to the pre-study examination and until the end of the study. * Reported weight loss or gain ≥ 10 % of bodyweight during the six months period before the pre-study examination * Pregnancy or breastfeeding declared by candidate * Smoking * Left-handed assessed by handedness questionnaire. This is to control for brain's lateralisation effects (activation in one side of the brain) that may show variations between left and right handed participants. * Participation in another clinical or research study within the previous 3 months of the study * Cannot lie flat or exceeding the scanner bed weight limit of 250 kg. * Poor understanding of the spoken and/or written English language